Sanada Vs Atobe

He was down 4-0 against Sanada constantly using Mountain (yes like in the technique), that was not toying that was dominating with a technique which got destroyed by Atobe shortly after.

Sure I'm just guessing, but considering Sanada uses FuuRinKaZan when he's in a pinch, one can guess that he must be weaker than Atobe without it. So both without their 'special techniques' should result in Sanada losing, if he doesn't swallow his pride and fully uses SOSA.

No, He only used Mountain against Atobe in the 3rd game. He used just his skill to win the 2 games before that.

The fact that he "said" Mountain, proves that its the first time he is using it. Every anime is the same way. They say their technique for only the first time. (unless it is a recap of the previous episode/chapter.)

No, He announced it again in the next chapter, to recap what he did in the previous chapter. Notice he doesn't say it anymore after that.

Uh no? He doesn't announce it one time, but you can pretty much guess it's because somebody speaks at that moment (about regaining pride and so on).
In Chapters 228-230 he uses Fire 5 times and announces it 4 times, it really seems to be his personal quirk.
And Fire is easy to identify after the first time.